"Users of the "old" high-dosage birth control pills experienced relatively severe side effects. However, many of these pills were generally considered non-abortifacient in their two-fold ("biphasic") modes of action. The pills would thicken cervical mucus and inhibit ovulation, but they would generally not inhibit implantation of the blastocyst (the five-day old, 256-cell developing human being) in the uterine lining. However, the new low-dosage pills are "triphasic." They have three modes of action; they thicken cervical mucus, inhibit ovulation, and block implantation. Therefore, the "new" Pills are all abortifacient in nature. The Department of Health and Human Services (HHS), in its 1984 pamphlet entitled "Facts About Oral Contraceptives," said that "Though rare, it is possible for women using combined pills (synthetic estrogen and progestogen) to ovulate. Then other mechanisms work to prevent pregnancy. Both kinds of pills make the cervical mucus thick and 'inhospitable' to sperm, discouraging any entry to the uterus. In addition, they make it difficult for a fertilized egg to implant, by causing changes in Fallopian tube contractions and in the uterine lining. These actions explain why the minipill works, as it generally does not suppress ovulation.""